Glev Blog

Security Debt: The invisible threat in your codebase

Written by Rodolphe Mas | Oct 8, 2025 10:27:50 AM

Every modern engineering team moves fast. New features ship weekly, security scanners run daily, dashboards glow green — and everyone assumes the software is safe enough.

But beneath this rhythm, something invisible is growing.

Every unresolved vulnerability, every “we’ll fix it later” decision, every outdated dependency quietly adds to a hidden liability in your codebase: security debt.

Unlike a bug that breaks a build, this debt doesn’t stop delivery. It just waits — accumulating risk, compounding complexity, and silently expanding your exposure.

If technical debt slows you down, security debt drains your resilience — and your resources.

What is security debt, really?

Security debt is the sum of known but unresolved vulnerabilities living in your running software — across your own code, your dependencies, and your infrastructure-as-code.

Each vulnerability is a potential entry point for an attacker. Once it reaches production, it becomes a liability — a weakness you now “owe” to the future.

It’s not theoretical risk; it’s a measurable backlog of vulnerabilities that already exist in production.

The problem is not that you have security debt — everyone does — but that you might not even know how much.

According to Veracode’s State of Software Security 2024 report:

  • 71% of organizations have flaws unremediated for over a year
  • 46% carry persistent high-severity vulnerabilities — critical debt that represents active exposure.

What differentiates one company from another isn’t whether they have security debt, but whether they can see it, measure it, and manage it.

Why we call it “debt”

Security debt behaves just like financial or technical debt — but with higher stakes.

When teams postpone fixes, skip reviews, or delay patching vulnerable components, they’re taking an invisible loan.

It buys short-term velocity, but adds long-term cost.

The interest accumulates as:

  • The code context fades, making fixes harder later.
  • Dependencies multiply, spreading the same vulnerability across multiple services.
  • Urgent fixes require coordination, downtime, or rewriting forgotten modules.

Each “later” adds friction, cost, and risk.

And unlike technical debt, which mainly slows you down, security debt can cost you business — through incidents, compliance gaps, or lost trust.

We’ll explore those hidden costs in detail in our next article.

Where security debt comes from

Every software company generates security debt — often faster than they realize.

  1. Velocity pressure: shipping fast means deferring non-blocking fixes.
  2. Fragmented tooling: findings come from many scanners and reports.
  3. Limited context: developers see CVSS scores, not business impact.
  4. Dependency sprawl: open-source libraries and frameworks multiply the risk surface.
  5. Legacy systems: old code nobody dares to touch.
  6. Competing priorities: fixing vulnerabilities rarely wins against features.
  7. Tool fatigue: security tools generate more alerts than teams can triage.

Security debt isn’t a sign of negligence — it’s the natural byproduct of building software at scale.

But unmanaged, it grows beyond control.

Why it’s so hard to see

Security debt is invisible not because it’s small, but because it’s fragmented.

It lives across multiple, disconnected sources:

  • SAST scanners for first-party code,
  • SCA scanners for open-source dependencies,
  • Secrets detection tools,
  • IaC and container scanners,
  • Pentest reports,
  • Bug bounty submissions.

Each tool has its own format, scoring, and severity model. The result?

A scattered picture where no one truly knows the total amount of debt or its real business impact.

But the bigger issue isn’t fragmentation — it’s misprioritization.

Most scanners prioritize issues based on generic severity scores (like CVSS), not on how those issues actually affect your context.

So teams often fix “critical” vulnerabilities that may be irrelevant, while ignoring “medium” ones that expose sensitive data paths.

That’s how organizations end up creating more debt while trying to reduce it: by fixing the wrong issues first.

We discussed this in detail in our previous article: Generic triage doesn’t work. Contextual triage does.

Without contextual prioritization — based on code ownership, exploitability, and business criticality — you’re fighting the wrong battles.

The compounding effect: how security debt grows

Security debt doesn’t just sit still — it compounds.

Like interest on a loan, the longer you wait, the harder it becomes to pay down.

Imagine this timeline:

  • Day 0: a low-risk vulnerability is detected. It’s postponed.
  • Month 3: new features touch that code. Fixing it now impacts multiple services.
  • Month 6: an exploit is published. What was “low” becomes urgent.
  • Month 12: your customer or regulator requests proof of remediation. The original developer has left.

What was once a one-line fix now requires a full refactor, new tests, and coordination between teams.

That’s the hidden side of aging code:

  • Knowledge fades.
  • Context disappears.
  • The cost to fix grows.

When developers leave or technologies shift, nobody remembers why a vulnerable component was implemented that way. The remediation becomes riskier, slower, and more expensive.

In security terms, inaction carries an interest rate — and it’s often higher than you think.

Why this matters now

For years, security debt was an abstract notion. Today, it’s a strategic concern.

Three forces make it impossible to ignore:

  1. AI-driven development: more code is written, faster than ever — often without deep review.
  2. Dependency explosion: a single outdated library can compromise your entire stack.
  3. Regulatory pressure: frameworks like NIS2, DORA, and SEC disclosures make unaddressed vulnerabilities a compliance issue.

The faster you move, the faster your security debt grows.

And while financial debt is visible on a balance sheet, security debt remains invisible — until it costs you.

Manage the debt or it manages you

Every company carries security debt.

Most can’t say how much, where, or how fast it’s growing.

Recognizing it is the first step.

Quantifying and managing it is what protects your business.

Security debt isn’t just about exposure — it’s about cost:

  • The cost of delayed remediation,
  • The cost of compliance gaps,
  • The cost of lost trust and missed opportunities.

Understanding and reducing that cost starts with visibility.

Because what you can’t see, you can’t fix — and what you can’t fix, you’ll eventually pay for.

At Glev, we help engineering teams make their security debt visible, measurable, and we help them crush it.

Want to understand your own debt — and how to reduce it before it grows? Contact Glev's team right now 👇